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  Circuit with a capacitive element with method for testing the sameUSPTO Application #: 20070041145Title: Circuit with a capacitive element with method for testing the same Abstract: A circuit has an input terminal, an output terminal, a supply voltage terminal, a ground terminal and a useful circuit, wherein the useful circuit has a capacitive element with a first and a second capacitance terminal, wherein the capacitive element has a series connection of two series capacitors, which are connected to each other at an inner capacitance node, and an additional testing terminal coupled to the inner capacitance node, and designed such that at least one of the series capacitors is positioned between the additional testing terminal and the reference terminal comprising the input terminal, the output terminal, the supply voltage terminal and the ground terminal, related to current flow. (end of abstract)
Agent: Maginot, Moore & Beck Chase Tower - Indianapolis, IN, US Inventor: Reinhard Losehand USPTO Applicaton #: 20070041145 - Class: 361272000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070041145. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION: [0001] This application claims priority from German Patent Application No. 102005038895.7, which was filed on Aug. 17, 2005 and is incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention relates to a circuit with a capacitive element and a method for testing the same. DESCRIPTION OF THE RELATED ART [0003] ICs (IC=integrated circuit) are increasingly required to integrate electronic devices, which are at present mounted outside the integrated circuit on a board. This leads to a reduction of the space requirements for a circuit, which is to perform a predetermined functionality. Thereby, increasingly, capacitors are integrated, for example, in silicon high-frequency ICs. Thus, the number of required devices in a high-frequency circuit or high-frequency system, respectively, can be reduced. [0004] Normally, the capacitors integrated in the silicon high-frequency IC or chip, respectively, are designed such that they have a higher breakdown voltage than the semiconductors or resistor devices used in the integrated circuit. [0005] However, the capacitors integrated in the chip can often not be provided with voltages as high as their breakdown voltage when testing the device. Thus, it is harder or impossible to detect defective capacitors. Those defective capacitors can represent a reliability risk for an operation of the integrated circuit. [0006] This reliability risk causes a limitation of the overall size of used capacitors in an integrated circuit to a value, where a probability of a failure of one of the used capacitors remains low. This has the effect that larger capacitors are frequently mounted at the external terminals or outside the integrated circuit on a circuit board, respectively, as discrete capacitors, and are connected with those integrated circuits via their external terminals. Thus, due to the external capacitors, which are to be provided on the printed circuit board, increased space requirements result on a printed circuit board for a circuit with predetermined functionality. SUMMARY OF THE INVENTION [0007] It would be advantageous to provide a circuit with a capacitive element, which has improved reliability, and to provide a method for testing the circuit having improved reliability. [0008] In accordance with a first aspect, the present invention in at least one embodiment provides a circuit having an input terminal into the circuit for feeding in a useful signal to be processed by the circuit, an output terminal out of the circuit for outputting a useful signal processed by the circuit, a useful circuit connected between the input terminal and the output terminal and designed to process the useful signal, a supply voltage terminal for supplying a supply voltage to the useful circuit, a ground terminal connected to the useful circuit, wherein the useful circuit has a capacitive element with a first and a second capacitance terminal, wherein the capacitive element has a series connection of two series capacitors, which are connected to each other at an inner capacitance node, wherein the first or the second capacitance terminal is coupled to a reference terminal comprising the input terminal, the output terminal, the supply voltage terminal or the ground terminal, such that direct current or alternating current with a frequency where the series capacitors have a resistance of more than 500 .OMEGA. can flow, and an additional testing terminal, which is coupled to the inner capacitance node, and which is formed such that at least one of the series capacitors is positioned between the testing terminal and the reference terminal related to current flow. [0009] In accordance with a second aspect, the present invention in at least one embodiment provides a method for testing a circuit, wherein the circuit has an input terminal into the circuit for feeding in a useful signal to be processed by the circuit, an output terminal out of the circuit for outputting a useful signal processed by the circuit, a useful circuit connected between the input terminal and the output terminal and designed to process the useful signal, a supply voltage terminal for supplying a supply voltage to the useful circuit, a ground terminal connected to the useful circuit, wherein the useful circuit has a capacitive element with a first and a second capacitance terminal, wherein the capacitive element has a series connection of two series capacitors, which are connected to each other at an inner capacitance node, and the first or the second capacitance terminal is coupled to a reference terminal comprising the input terminal, the output terminal, the supply voltage terminal or the ground terminal, such that direct current or alternating current with a frequency where the series capacitors have a resistance of more than 500 .OMEGA. can flow, and an additional testing terminal, which is coupled to the inner capacitance node, and which is designed such that at least one of the series capacitors is positioned between the testing terminal and the reference terminal, related to current flow, having the steps of applying a potential difference between the reference terminal and the additional testing terminal and determining a test result based on current flowing into the circuit at the additional testing terminal due to applying the potential difference. [0010] The present invention is based on the knowledge that a capacitive element in a circuit can be designed in the form of a series connection of two capacitors, so that an inner capacitance node, where the two series capacitors are connected to each other, can be connected to a testing terminal. A terminal at one of the two series capacitors, which is not directly connected to the inner capacitance node, can then be coupled to a reference terminal, which comprises, for example, an input terminal, an output terminal, a supply voltage terminal or a ground terminal, so that when testing the series capacitors, voltage can be applied directly to one of the two series capacitors, which can also be higher than a voltage strength of a further device in the circuit. [0011] Thus, a series capacitor can be tested with a higher voltage or a higher breakdown voltage, respectively, than another, for example non-capacitive device in the circuit. [0012] By testing a series capacitor with a higher breakdown voltage, weaknesses in the breakdown strength of the series capacitor can be detected at an early stage. This can have the effect that chips, on which the implemented series capacitors show weaknesses of a breakdown strength during testing, are no longer delivered, or only used in devices where lower quality is required from the chips. Thus, the reliability of the series capacitor and thus the capacitive element, which comprises the series capacitor, is increased due to the improved tested breakdown strength. [0013] The increased reliability of the series capacitors has the effect that more capacitors can be integrated in a chip, since the series capacitors now represent a significantly lower reliability risk for perfect operation of the circuit implemented on the chip. This allows a reduction of space requirements for a circuit having predetermined functionality, since now more capacitors can be integrated in one chip. Thus, reduced space requirements of a circuit according to an embodiment of the present invention offer, for example, a more flexible application in portable devices. [0014] Additionally, capacitors or series capacitors, respectively, with higher capacitance and thus larger areas can be integrated on a chip, since a reliability risk of the capacitors with larger areas is reduced due to improved testing of the breakdown strength of the series capacitors. [0015] Additionally, an improved protection results for the other devices in an integrated circuit, where the series capacitors with increased breakdown strength are used, since the series capacitors can now be connected directly to two terminals in a circuit according to an embodiment of the present invention between which a potential difference is applied for testing the series capacitors. [0016] Then, in the circuit according to an embodiment of the present invention, the voltage for testing the breakdown strength of the series capacitors no longer drops at the other devices having lower breakdown strength. Thus, a probability that the other devices with lower breakdown strength are destroyed when testing the series capacitors by the higher voltages for testing the series capacitors is reduced. [0017] Even a disadvantageous increase of the reliability risk due to arranging a capacitive element in the form of the two series capacitors, which causes an increase of the capacitance values implemented on the chip, is compensated by an increased reliability of the series capacitors to the improved testing of the series capacitors. [0018] Specifically, this means, for example, that for implementing a capacitive element with a value of 1 nF, two series capacitors are arranged in a series connection, each with a value of 2 nF. Here, a probability that one of the two capacitors with a capacitance value of 2 nF has a weakness with regard to its breakdown strength is higher than in a chip with only one capacitor with a value of 1 nF. However, the inner capacitance node where the two series capacitors with the value of 2 nF are connected can be connected directly to a testing terminal, so that a voltage for testing the breakdown strength can be applied directly to the series capacitors. Since the inner node can be connected directly to the external additional testing terminal, higher voltages can be applied to the testing terminal and thus to the series capacitors with a value of 2 nF, than to the capacitor with a capacitance value of 1 nF. Thus, the reliability of the capacitive element consisting of the two series capacitors of each 2 nF is higher than in the capacitive element, which has only one capacitor of 1 nF, due to the improved testing of the breakdown strength with increased voltage. BRIEF DESCRIPTION OF THE DRAWINGS [0019] These and other advantages and features of the present invention will become clear from the following description taken in conjunction with the accompanying drawings, in which: Continue reading... Full patent description for Circuit with a capacitive element with method for testing the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Circuit with a capacitive element with method for testing the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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